/Engine/Source/Runtime/Engine/Classes/GameFramework/HUD.h
Sample usage:   TArrayActorsInSelectionRect;
    Canvas->GetActorsInSelectionRectangle(FirstPoint,SecondPoint,ActorsInSelectionRect);
OutActors The actors that are within the selection box according to selection rule
void GetActorsInSelectionRectangle ( [TSubclassOf](API\Runtime\CoreUObject\Templates\TSubclassOf)< [AActor](API\Runtime\Engine\GameFramework\AActor) > ClassFilter, const FVector2D & FirstPoint, const FVector2D & SecondPoint, [TArray](API\Runtime\Core\Containers\TArray)< [AActor](API\Runtime\Engine\GameFramework\AActor) * > & OutActors, bool bIncludeNonCollidingComponents, bool bActorMustBeFullyEnclosed )